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SDK-85 Restoration – Part 1

Released in 1977, the SDK-85 was Intel’s development board for their new 8085 CPU. Unlike the 8080 on which it was based, the 8085 only required a single 5v power source making it ideal for small systems. Along with the 8085, the board contains a hex keypad, 7 segment displays, 256 bytes of RAM (Upgradable to 512 !) and a small monitor program in the 2k of ROM. There was also an interface for connection of a teletype.

One of the nice features of the SDK-85 is it has a large prototyping area for adding your own circuits to upgrade the system. However a downside of this is that when these boards do come up for sale, they often have their previous owners experiments soldered in. This was the case on my SDK-85 that I recently acquired…

This board was purchased on Ebay and came with a couple of extra components & connectors in the prototype area. My plan was to remove these, clean up the board and add sockets for the additional driver & ROM IC’s…

The images above show the stages of the board clean up and addition of the new sockets. I decided to also change the 40pin socket that had been fitted for the optional RAM expansion. Nothing wrong with it but just wanted one that matched the other sockets. The next step is to add some solderless breadboards on top of the prototype area. This will allow the addition of test circuits & experiments but can easily be removed if I want to restore the back to the original spec. I’ll cover this once I’ve ordered the breadboards 🙂